Catalysts On Substrates And Methods For Providing The Same

ABSTRACT

A method for providing a catalyst on a substrate is disclosed comprising providing a first washcoat comprising a soluble washcoat salt species, a polar organic solvent, and an insoluble particulate material, contacting the first washcoat with a substrate to form a coated substrate, and then contacting the coated substrate with a second washcoat comprising an oxide or an oxide-supported catalyst to physisorb, chemisorb, bond, or otherwise adhere the oxide or the oxide-supported catalyst to the coated substrate. Also disclosed is a catalyst on a substrate comprising: a substrate; an anchor layer comprising a soluble washcoat salt species, a polar organic solvent, and an insoluble particulate material; and a second layer comprises an oxide or an oxide-supported catalyst. The catalyst on a substrate can be in either green or fired form.

TECHNICAL FIELD

The present invention relates generally to catalysts on substrates andmethods for providing the same, and more particularly to oxide oroxide-supported catalysts on substrates and methods for providing thesame.

BACKGROUND

Developing highly active, supported catalysts is of continued andgrowing interest. Supported catalyst systems can aid in reducing airpollution from power plants, refineries, and other chemical processingplants in addition to being useful in many other industrialapplications. Supported catalyst systems can also be designed to reducevolatile organic compound (VOC) emissions from operations such as, forexample, printers, dry cleaners, paint shops, and plastic-mold shops.

Supported catalyst materials can be used for a variety of chemicaltransformations, such as, for example, in hydrodesulfurization,hydrogenation, methanation, methanol synthesis, ammonia synthesis,carbon monoxide oxidation, and various petrochemical processes.Moreover, expensive catalysts, such Pd or Pt based catalysts can besupported such that the catalyst can be recycled.

It can be desirable to apply a catalyst to a substrate to enhancedispersion of the supported catalyst. The substrate can function, forexample, as a form factor for the catalyst during operation. Currentmethods to apply catalysts onto supports and substrates, however, can belimited by incompatibilities (e.g. a lack of bonding capability) betweenthe catalyst material and the substrate. Such methods for manufacturingsupported catalysts can also ultimately lead to a loss of catalystdispersion and/or a loss of catalytic activity.

There is a need to address the aforementioned problems and othershortcomings associated with traditional catalyst materials and methods.

SUMMARY

The present disclosure relates to multilayered catalyst supports andmethods for the manufacture and use thereof. The present disclosureaddresses at least a portion of the problems described above through theuse of multilayered catalyst supports, and methods of making and usingthe disclosed multilayered catalyst supports.

In one embodiment, a method for providing a catalyst on a substrate isdisclosed comprising providing a first washcoat comprising a solublewashcoat salt species, a polar organic solvent, and an insolubleparticulate material, contacting the first washcoat with a substrate toform a coated substrate, and then contacting the coated substrate with asecond washcoat comprising an oxide or an oxide-supported catalyst tophysisorb, chemisorb, bond, or otherwise adhere the oxide or theoxide-supported catalyst to the coated substrate.

In another embodiment, a catalyst on a substrate comprising: a) asubstrate having at least one surface; b) an anchor layer contacting atleast a portion of the at least one surface, comprising a solublewashcoat salt species, a polar organic solvent, and an insolubleparticulate material; and c) a second layer positioned on at least aportion of the anchor layer oppositely disposed from the substrate,wherein the second layer comprises an oxide or an oxide-supportedcatalyst is described.

In yet another embodiment, a catalyst on a substrate comprising asubstrate having at least one surface, an anchor layer contacting atleast a portion of the at least one surface, and a second layerpositioned on at least a portion of the anchor layer oppositely disposedfrom the substrate, wherein the anchor layer comprises a first oxide,wherein the second layer comprises a second oxide or an oxide-supportedcatalyst, and wherein both the anchor layer and the second layercomprise substantially no binder is disclosed.

Additional aspects and advantages of the disclosure will be set forth,in part, in the detailed description and any claims which follow, and inpart will be derived from the detailed description or can be learned bypractice of the various aspects of the disclosure. The advantagesdescribed below will be realized and attained by means of the elementsand combinations particularly pointed out in the appended claims. It isto be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the disclosure.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate certain examples of the presentdisclosure and together with the description, serve to explain, withoutlimitation, the principles of the disclosure. Like numbers represent thesame elements throughout the figures.

FIG. 1 illustrates an exemplary embodiment of the invention.

DETAILED DESCRIPTION

The following description is provided as an enabling teaching of thedisclosure in its best, currently known embodiment. To this end, thoseskilled in the relevant art will recognize and appreciate that manychanges can be made to the various embodiments of the disclosuredescribed herein, while still obtaining the beneficial results of thepresent disclosure. It will also be apparent that some of the desiredbenefits of the present disclosure can be obtained by selecting some ofthe features of the present disclosure without utilizing other features.Accordingly, those who work in the art will recognize that manymodifications and adaptations to the present disclosure are possible andcan even be desirable in certain circumstances and are a part of thepresent disclosure. Thus, the following description is provided asillustrative of the principles of the present disclosure and not inlimitation thereof.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings:

As used herein, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to a “solvent” includes examples having two or moresuch “solvents” unless the context clearly indicates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not.

Disclosed are the components to be used to prepare the disclosedcompositions as well as the compositions themselves to be used withinthe methods disclosed herein. These and other materials are disclosedherein, and it is understood that when combinations, subsets,interactions, groups, etc. of these materials are disclosed that whilespecific reference of each various individual and collectivecombinations and permutation of these compounds may not be explicitlydisclosed, each is specifically contemplated and described herein. Thus,if there are a variety of additional steps that can be performed it isunderstood that each of these additional steps can be performed with anyspecific embodiment or combination of embodiments of the disclosedmethods.

As used herein, a “wt. %” or “weight percent” or “percent by weight” ofa component, unless specifically stated to the contrary, refers to theratio of the weight of the component to the total weight of thecomposition in which the component is included, expressed as apercentage.

As used herein, the term “coating” is intended to refer to a suspensionof components that, when applied to a substrate, can provide a highsurface area surface suitable for stabilizing one or more oxides oroxide-supported catalysts particles.

As used herein, the term “washcoat” is intended to refer to acomposition that can be applied to a substrate or a coated substrate.

As used herein, the terms “substrate” is intended to refer to a bodyonto which a coating and/or a washcoat can be deposited. A substrateincludes a monolith and can have any form and/or geometry, such as, forexample, honeycomb, stacked, coiled, woven, foamed, or a combinationthereof, and can be comprised of any suitable substance for the intendedapplication.

As used herein, the terms “nano” and “nano-particle” are intended torefer to particles having, in various aspects, at least one aspect withan average particle size of less than about 100 nm, less than about 10nm, or less than about 5 nm.

It is understood that the catalysts on substrates disclosed herein havecertain functions. Disclosed herein are certain structural requirementsfor performing the disclosed functions and it is understood that thereare a variety of structures that can perform the same function that arerelated to the disclosed structures, and that these structures willtypically achieve the same result.

Disclosed herein are catalysts on substrates and methods of makingcatalysts or supported catalysts on substrates. In various aspects ofthe present disclosure, a coating can be bound and/or adhered to a solidsubstrate, the coating having a composition and a means to bond and/oradhere to an oxide or an oxide-supported catalyst. The presentdisclosure allows for, in general, an oxide or an oxide-supportedcatalyst to be processed separately from a substrate and/or a coatedsubstrate thereby overcoming at a least some adverse effects that canoccur when the substrate, coated substrate, oxide, and/oroxide-supported catalyst are all processed together.

In one embodiment, a method for providing a catalyst on a substrate isdisclosed comprising providing a first washcoat comprising a solublewashcoat salt species, a polar organic solvent, and an insolubleparticulate material, contacting the first washcoat with a substrate toform a coated substrate, and then contacting the coated substrate with asecond washcoat comprising an oxide or an oxide-supported catalyst tophysisorb, chemisorb, bond, or otherwise adhere the oxide or theoxide-supported catalyst to the coated substrate.

In another embodiment, a catalyst on a substrate comprising: asubstrate; an anchor layer comprising a soluble washcoat salt species, apolar organic solvent, and an insoluble particulate material; and asecond layer comprising an oxide is described.

According to the invention, the catalyst on a substrate can be in eithergreen or fired form.

Substrate

A substrate for use in the present disclosure can comprise any suitablematerial. Given that the substrate itself need not be exposed to thecatalyst or the supported catalyst processing conditions, which can, invarious aspects, adversely affect at least some substrate materials, thepresent disclosure allows for any or substantially any substrate to beused. The substrate can comprise an inorganic material, an organicmaterial, or a combination thereof

In one aspect, the substrate comprises a plurality of inner channelshaving surfaces defined by porous walls and extending through thesubstrate from a first face to a second face. The substrate can be amonolith, such as, for example, a honeycomb structure. Other monolithsubstrates can comprise pores of any shape, and a honeycomb, hexagonalstructure is not a limiting feature of the present disclosure. Asubstrate, such as a monolith, can comprise any material suitable forbeing coated. In one aspect, a substrate comprises an inorganicrefractory material. In other aspects, a substrate comprises a glass, aceramic, a glass-ceramic, or a combination thereof. In various specificaspects, a substrate comprises cordierite, aluminum titanate, titania,alumina, such as, for example, α-alumina, γ-alumina, or other ceramicmaterial and/or a combination thereof. In yet other aspects, a substratecomprises a carbon material, such as, for example, a glassy carbon. Instill other aspects, a substrate comprises a metal, such as, forexample, aluminum. In still other aspects, a substrate comprises apolymeric material, such as, for example, a thermoplastic. It should benoted that the present disclosure is not limited to the specificsubstrate materials recited herein and can thus comprise any suitablematerial, including, for example, a combination of any two or morerecited materials. In various aspects, the substrate can comprise asolid material, a sponge, such as, for example, a metal or plasticsponge, a sintered material, or a combination thereof As such, asubstrate can comprise, in various aspects, a porous material, anon-porous material, a semi-porous material, or a combination thereof

In one aspect, a substrate can have a porous surface, and uponapplication of a coating to the porous surface, at least a portion of acoating can penetrate into the porous surface. In a specific aspect, atleast a portion of a coating can penetrate at least a portion of thepores of a substrate. In another aspect, a coating can be applied to theporous surface of a substrate such that all or substantially all of thecoating slurry penetrates into the porous surface, wherein anon-continuous coating is formed on the substrate surface. The term“coating” applies to all of these circumstances.

If a substrate comprises voids, channels, and/or other openings, excesscoating material, if present, can optionally be removed afterapplication using any suitable technique, such as, for example, blowingwith compressed air.

In one aspect, once a substrate, such as a monolith, has been coatedwith, for example, a washcoat, the substrate can be dried, allowed todry, and/or calcined. The parameters of a particular drying and/orcalcining step can vary and one of skill in the art could readily selectappropriate drying and/or calcining steps for a particular substrate andcoating material. The substrate, for example, an uncoated substrate or asubstrate coated with a washcoat, can be processed, in various aspects,separately from the catalyst or the supported catalyst. In certainapplications, this can be an advantage of the present disclosure.

It is understood that the substrate of the disclosure can be used incombination with the methods, products, and applications of thedisclosure.

First Washcoat

In various aspects, a washcoat of the present disclosure can comprise,for example, any salt species that is at least partially soluble in oneor more polar organic solvents, water, or a combination thereof. In oneaspect, the soluble washcoat salt species is at least partially solublein water. In one aspect, the soluble washcoat salt species is at leastpartially soluble in a polar organic solvent. In another aspect, thesoluble washcoat salt species is substantially soluble in a polarorganic solvent. In various aspects, the soluble washcoat salt specieshas a solubility greater than about 1 ppm, such as, for example, about1.5, 2, 5, 10, 50, 100, 200, 400, 500, 800, 1,000, 1,500, 2,000, 3,000,or 10,000 ppm; or greater than about 1,000 ppm, for example, about1,000, 1,500, 2,000, 3,000, 5,000, 10,000, 15,000, 20,000, 30,000,50,000 ppm or more in water, a polar organic solvent, or a combinationthereof. It should be understood that the solubility of any particularsoluble washcoat salt species can vary depending upon such factors aspH, temperature, the particular counterion of a salt species present,and/or the nature and polarity of the solvent employed, and the presentdisclosure is not intended to be limited to any particular level ofsolubility. It should be noted that the solvent of the presentdisclosure can comprise a polar solvent, water and that the solublewashcoat salt species should be at least partially soluble in theparticular solvent and/or combination of solvents employed.

In other aspects, the soluble washcoat salt species can form a colloidalsuspension and/or a sol in the particular solvent and/or combination ofsolvents employed, provided that at least a portion of the solublewashcoat salt species is at least partially ionized.

In one aspect, the soluble washcoat salt species comprises at least onesoluble cationic species and at least one soluble anionic species. Invarious aspects, the soluble cationic species comprises a transitionmetal, an alkali metal, an alkali earth metal, a rare earth metal, or acombination thereof In various aspects, the soluble anionic speciescomprises a nitrate, a halide, a sulfate, a sulfite, a nitrite, aphosphate, a carbonate, an oxalate, a carboxylate (e.g., a formate or anacetate), or a combination thereof In other aspects, the soluble anionicspecies comprises a polyoxometalate (e.g., [PMo₁₂O₄₀]³⁻) wherein atransition metal species is anionic and a counter ion (e.g., [NH₄]¹⁺) iscationic. In such an aspect comprising a polyoxometalate, such as, forexample, [PMo₁₂O₄₀]³⁻, a metal oxide, such as, for example, molybdenumoxide, can act as a binder.

In various aspects, the soluble washcoat salt species comprises an ironcompound, a zinc compound, a copper compound, an aluminum compound, or acombination thereof In a specific aspect, the soluble washcoat saltspecies comprises an iron compound, such as, for example, iron nitrate,iron sulfate, iron chloride, or a combination thereof While not wishingto be bound by theory, it is believed that iron oxide can promotecatalysis when used with certain metal catalyst particles dispersed onit and the presence of iron can help maintain small, high surface area,metal catalyst particles. In other aspects, the soluble washcoat saltspecies can comprise a hydroxide, such as, for example, iron hydroxide,an oxyhydride, or a combination thereof It should be noted that suchoxide compounds can have limited solubility in water, a polar organicsolvent, or a combination thereof, and that a suspension of at leastpartially soluble and/or partially ionized oxide compounds can be usedeither alone, or in combination with other soluble washcoat saltspecies.

The concentration of the soluble washcoat salt species can vary,depending upon the specific salt species, polar organic solvent, andconditions such as, for example, temperature and/or pH. In variousaspects, the concentration of the soluble washcoat salt species canrange from about 0.01 M to the maximum solubility limit of the salt; orfrom greater than about 0.01 M to about 10 M, for example, about 0.01,0.02, 0.05, 0.08, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 9or 10 M. In other aspects, the concentration of the soluble washcoatsalt species can be less than about 0.01 M or greater than about 10.0 M,and the present disclosure is not intended to be limited to anyparticular concentration range. In one specific aspect, the solublewashcoat salt species comprises an iron nitrate and is present at aconcentration of about 1.6 M. In other aspects, the soluble washcoatsalt species can comprise multiple salt species having the same ordifferent cations.

The polar organic solvent of the present disclosure can comprise anysuitable polar organic solvent for at least partially solvating and/ordissolving the soluble washcoat salt species. In various aspects, thepolar organic solvent can comprise an ethylene glycol monoethyl ether,an ethylene glycol monomethyl ether, a diethyl glycol monoethyl ether, acellusolve compound, or a combination thereof In other aspects, thepolar organic solvent can comprise any ethylene glycol derivative thatcan function as described herein.

The insoluble particulate material of the present disclosure cancomprise any material suitable for use in the intended application. Inone aspect, the insoluble particulate material can comprise asubstantial portion of and/or the largest volume fraction of a washcoatcomposition. In various aspects, the insoluble particulate material canact as a binder and the coating composition requires no addition binderand/or binder materials. In one aspect, the insoluble particulatematerial comprises an oxide, such as, for example iron oxide, zincoxide, tin oxide, ceria, titania, alumina, silica, spinel, perovskite,or a combination thereof In yet other aspects, the insoluble particulatematerial can comprise a carbide, a nitride, a particulate carbonaceousmaterial (e.g., activated carbon and/or carbon black), or a combinationthereof The insoluble particulate material can comprise a plurality ofindividual insoluble particulate materials having the same or differentcomposition. In one aspect, the insoluble particulate material comprisesan oxide, wherein the oxide comprises the same cation (e.g., metal) asthe soluble washcoat salt species, or of at least one salt species ofthe soluble washcoat salt species if multiple salt species are present.In a specific aspect, the insoluble particulate material comprises aniron oxide.

In one aspect, a washcoat and/or an insoluble particulate material canitself be at least partially catalytically active. In a specific aspect,an insoluble particulate material is an oxide that exhibits catalyticactivity. In another aspect, a washcoat and/or an insoluble particulatematerial does not exhibit any substantial catalytic activity.

The particular composition and/or phase of an insoluble particulatematerial can vary. In various aspects, the insoluble particulatematerial comprises alpha, gamma, delta, eta, theta, kappa, rho, and/orchi alumina, silica, silica aluminate, zeolite, silica-magnesia,titanium oxide, zirconium oxide, or a combination thereof

The contemplated substrate coating can be of any desired thickness for aparticular application. Typically, given that the substrate coating canserve to anchor the catalyst, the coating can have a thickness such thatthe optimal catalyst dispersion and exposure is achieved. In general,the present disclosure can allow for very thin coatings. Thicknesses ofthe coating can depend, in various aspects, on the particle size of thecoating material. Again, the desired particle size of the coatingmaterial should be selected or processed based on the desired thicknessof the catalyst and catalyst support particles such that good adhesionis achieved. Contemplated thicknesses for the coating include, withoutlimitation, about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.3,1.4, 1.5, 1.6, 1,8, 2, 2.3, 2.5, 2.7, 3, 3.5, 4, 5, 6, 8, 9, or 10 μm.The thickness of a coating can also be about 0.1, 0.2, 0.5, 0.8, 1, 2,3, 4, or 5 mm. In one aspect, the thickness of a coating can be lessthan about 5 mm. Even thinner coating can include thicknesses of about6, 7, 8, 9, 12, 20, 30, 40, 50, 60, 70, 80, 90, and 95 nm, and thepresent disclosure is not intended to be limited to any particularcoating thickness.

The substrate coating can be bound to a catalyst or a supported catalystthrough any appropriate means, for example, noncovalent and/or covalentbonding, physical adsorption, chemisorption, and/or any other adhesionmechanism. In various aspects of the present disclosure, the catalystsupport can comprise a substance capable of hydrogen bonding with thesubstrate coating. In these examples, the catalyst support can compriseat least one hydrogen bond donor and/or at least one hydrogen bondacceptor. If a hydrogen bond acceptor is present, the hydrogen bondacceptor can comprise an electronegative atom. Typical electronegativeatoms capable of hydrogen bonding include, without limitation, fluorine,oxygen, and nitrogen. If any of the aforementioned hydrogen bondacceptors are present, they can be bonded to a metal atom. If oxygen ispresent, for example, the oxygen can be bonded to a metal to form ametal oxide. Examples of metals oxides contemplated for use in at leasta portion of the substrate coating include, without limitation, ceriumoxides, copper oxides, zinc oxides, aluminum oxides, and/or anycombination thereof Other specific examples include, without limitation,TiO₂, Al₂O₃, γ-Al₂O₃, SiO₂, MgO, ZnO, Fe₂O₃, and/or any combinationthereof A further example comprises yttria and zirconia, such as, forexample, yttria-stabilized zirconia.

Although not wishing to be bound by theory, if a hydrogen bond existsbetween the catalyst support and the substrate coating, the bond neednot always be either the same type of bond and need not always bepresent. In one aspect, a powder catalyst support material comprises ametal oxide, wherein the powder is bonded to a substrate coatingcomprising a metal oxide through a hydrogen bond. After calcination ofthe powder and substrate coating, the hydrogen bond can form a metaloxygen bond with the dehydration.

Second Washcoat

The present disclosure comprises, in various aspects, a second washcoat.In various aspects, the second washcoat can comprise an oxide. In oneaspect, the second washcoat comprises the same or substantially the samecomposition as the first washcoat. In another aspect, the secondwashcoat comprises an oxide material different from that and/or thoseutilized in the first washcoat. In yet another aspect, the secondwashcoat comprises an oxide-supported catalyst. The second washcoat cancomprise any material suitable for catalyst immobilization. The secondwashcoat can, in various aspects be capable of binding to a substratecoating. In general, it can be advantageous in certain applications tohave a second washcoat and a first washcoat comprised of similar sizedparticles such that, for example, good adhesion is obtained.

A second washcoat can be bound to a coated substrate, and/or a catalystthrough any appropriate means. In certain aspects, a second washcoat anda coating and/or catalyst may be bound through an ionic, metallic,covalent, noncovalent, electrostatic, physical, and/or any otherchemical or physio-chemical bonding means. It is not necessary that achemical bond or any particular type of bond be formed, provided thatthe second washcoat and/or catalyst sufficiently adhere to, for example,a substrate, so as to remain stable during the intended application. Thepresent disclosure is not intended to be limited by the exact nature ofthe adhesion between the coated substrate and/or catalyst and thecatalyst support. In one aspect, the bonding means that exists betweenthe catalyst and the second washcoat composition is of a nature suchthat substantial wt. % loss of the catalyst does not occur during theapplication of the catalyst material.

In one aspect, a second washcoat, such as, for example, anoxide-supported catalyst, can be bound to a coated substrate through anyappropriate means, for example, noncovalent and/or covalent bonding,physical adsorption, chemisorption, and/or any other adhesion mechanism.In various aspects of the present disclosure, the oxide or theoxide-supported catalyst can comprise a substance capable of hydrogenbonding with the coating of the coated substrate. In such aspects, anoxide-supported catalyst powder can comprise at least one hydrogen bonddonor and/or at least one hydrogen bond acceptor. If a hydrogen bondacceptor is present, the hydrogen bond acceptor can comprise anelectronegative atom. Typical electronegative atoms capable of hydrogenbonding can comprise, without limitation, fluorine, oxygen, andnitrogen. If any of the aforementioned hydrogen bond acceptors arepresent, they can optionally be bonded to a metal atom. If oxygen ispresent, for example, the oxygen can be bonded to a metal to form ametal oxide. Examples of metals oxides contemplated for use in at leasta portion of the catalyst or supported catalyst include, withoutlimitation, cerium oxide, copper oxide, zinc oxide, aluminum oxide,and/or any combination thereof Other specific examples include, withoutlimitation, TiO₂, Al₂O₃, γ-Al₂O₃, SiO₂, MgO, ZnO, Fe₂O₃, and/or anycombination thereof. A further example comprises yttria and zirconia,such as, for example, yttria-stabilized zirconia.

Although not wishing to be bound by theory, a hydrogen bond between asecond washcoat comprising, for example, an oxide-supported catalyst anda coated substrate can be intermittent and/or can vary. In one aspect, asecond washcoat comprises a metal oxide, wherein the oxide-supportedcatalyst is bonded to a coating of a coated substrate comprising a metaloxide through a hydrogen bond. After calcination of a second washcoatand substrate coating, the hydrogen bond can form a metal oxygen bond.

In one aspect, the first washcoat forming the first or anchor layer, andthe second washcoat comprising an oxide-supported catalyst cansufficiently adhere to each other to remain durable during operation,without the need for a binder material to be added to either of thewashcoat compositions and/or be applied to the substrate or coatedsubstrate.

In one aspect, the thickness of a layer formed from the second washcoatcan be any suitable thickness for an intended application. In variousaspects, the thickness of a second layer can range from about 1 nm toabout 5 mm, from about 1 μm to about 1 mm, from about 5 μm to about 3mm, or any combination of ranges therefrom. In other aspects, thethickness of a second layer can be thinner than about 1 μm or thickerthan about 5 mm, and the present disclosure is not intended to belimited to any particular thickness. In another aspect, the combinationof the thickness of an anchor layer formed from the first washcoat, andthe thickness of a second layer formed from a second washcoat are lessthan about 5 mm.

The second washcoat can, in various aspects, comprise particles orspecies of any desired shape and size. The application at hand can oftenhelp determine a desired supported catalyst powder size and shape. Ingeneral, the size and shape of the components of the second washcoat candepend at least partially on the method of preparation. In variousaspects, a second washcoat can comprise particles of colloidal size,e.g. between about 1 nm and about 1 μm. In such aspects, a finecolloidal particle size can be desirable to match the size of thesupported catalyst powder to the size of a substrate coating material,thereby, for example, enhancing adhesion properties. Exemplary colloidalparticle sizes include, without limitation, about 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 12, 14, 16, 18, 22, 30, 33, 37, 50, 60, 70, 80, 90, 100, 150,150, 300, 500, 600, 700, 900, 950 nm, and any combination thereof. Otherlarger particles can also be suitable for use in the present disclosure,including, without limitation, particles with sizes of about 1, 1.5, 2,2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6,7, 8, 9, 10, 11, 12, 13, 14, or 15 μm,and any combination thereof Larger particles can be reduced in size, ifdesired, by methods well-known in the art, such as ball-milling. Thecatalyst can be located in the interior and/or exterior of the secondwashcoat. It should be noted that each of the particulate materialsutilized in the various aspects of the disclosure can havedistributional properties, and as such, the size of any particle cancomprise a range of individual particle sizes. As such, any individualsize, range of sizes, and/or distribution of sizes are appropriate andintended to be covered by the disclosure.

Catalyst

The present disclosure can comprise, in various aspects, one or morecatalysts. Any catalytic species compatible with the washcoats,substrates, coated substrates, and/or methods described herein issuitable. In some aspects, a desired catalyst is one that can benefitfrom immobilization (e.g. enhanced dispersion), for example, catalystsused in hydrodesulfurization, hydrogenation, methanation, methanolsynthesis, ammonia synthesis, carbon monoxide oxidation, carbon-carbonbond forming reactions, and various petrochemical processes.

In one aspect, catalysts contemplated for use in various embodiments ofthe present disclosure can be, for example, redox catalysts (catalyststhat are oxidized and/or reduced during a catalytic cycle). In anotheraspect, such redox catalysts can comprise at least one inorganicelement. Given that transition metal elements, in particular, can have avariety oxidation states, a catalyst, in various aspects, can compriseone or more individual transition metal elements. An exemplary catalystcan comprise: Cr, Mn, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Cd, Ru, Pd, Pt, Rh,V, Mo, Co, Os, Ir, or a combination thereof Other suitable catalysts cancomprise elements from, for example, the poor metal group including,without limitation, Al, Si, Ga, In, or a combination thereof Multiplecatalysts and/or multi-metallic catalysts can also be utilized invarious aspects of the disclosure.

Other catalysts contemplated for use in the present disclosure include,without limitation, metal oxide catalysts. Specific examples includecatalysts wherein the metal ion component comprises Cu, Ce, Zn, Pd, andRh. Metal oxide catalysts comprising the aforementioned metal ioncomponents can comprise CuO—CeO₂, CuO—ZnO, Pd/Cu/ZnO, Pd/CuO/ZnO, Al₂O₃or a combination thereof Other aspects include catalysts comprising Rhand Al₂O₃. In one aspect, a catalyst comprising Rh and Al₂O₃ includescompositions wherein Rh is present in, for example, about 1 wt. % in thebulk catalyst composition. The specific concentration of a particularcatalyst species in a catalyst composition, a washcoat composition, or acoated substrate can vary, for example, from about 0.1 wt. % to about 99wt. %, from about 1 wt. % to about 80 wt. %, or from 1 wt. % to about 60wt. %, depending upon such factors as the intended application or levelof catalyst dispersion, and the present disclosure is not intended to belimited to any particular concentration of catalyst. In other aspects,an organometallic catalyst can be utilized. In certain aspects, if acalcination temperature is not sufficiently high to decompose any or allorganic material that can be present, an organometallic catalyst can beutilized.

Any method for making a catalyst that is suitable with the methods andsupported catalysts on substrates disclosed herein can be used. Theaforementioned catalysts can be made, for example, using methods wellknown in the art. One such method, as not to limit the presentdisclosure, can comprise contacting two metal salts to form acatalytically active species and/or a catalyst precursor which can laterbe activated. In other aspects, after a supported catalyst on asubstrate is processed, an activation and/or stabilization procedure canbe carried out. A catalyst precursor can be treated, for example, suchthat an active catalyst is generated. One such method comprisesreduction of a catalyst precursor to form an active catalyst. In variousaspects, the reduction can be carried out with a flow of gas. In anotheraspect, a powdered metal salt comprising a halogen, typically Cl, iscalcined to form a metal oxide, and is subsequently reduced andactivated with a flow of H₂ gas. In this aspect, the H₂ gas can becarried in another inert gas, such as, for example, helium gas.

Catalyst loading in and/or on the second washcoat can be any appropriatewt. % of the bulk powder composition. In one aspect, the catalystloading in and/or on the second washcoat can be, for example, 0.5, 1,1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 14.5, 16, 20, 21, 23,24, or 25 wt. % of the bulk powder composition.

The catalyst, supported catalyst, and/or the second washcoat can becharacterized, if desired, using methods well known in the art. Forexample, surface areas of catalysts can be estimated by a N₂ adsorptionmethod. Estimation of the surface area of a supported catalyst can beuseful to identify structure property relationships, but the presentdisclosure does not intend to be limited by surface areas of supportedcatalyst compositions. Further characterization can be carried outusing, for example, X-ray powder diffraction. Infrared spectroscopy canalso be useful in determining catalyst activity. If, for example, aparticular catalyst of the present disclosure can oxidize CO, then IRspectroscopy can be used to monitor the disappearance of the stretchingfrequency attributable to the sp hybridized bond of CO. While suchtechniques can be useful to estimate the activity of a supportedcatalyst, the present disclosure is not intended to be limited by anyspecific catalytic activity of a supported catalyst composition.

Any appropriate method to manufacture the supported catalyst of thepresent disclosure can be used. In one aspect, the physico-chemicalproperties of a supported catalyst can be linked to a preparationmethod. As such, given that the present disclosure is contemplated foruse in a variety of applications, the preparation method is not alimiting feature of the present disclosure.

Conventional methods that can be employed for supporting a catalyst onand/or in a catalyst support can comprise deposition-precipitation,co-precipitation, vapor deposition, zeolite formation, chemisorption,physisorption, chemi-/physi-sorption, impregnation methods, wetimpregnation, dry impregnation techniques, and combinations thereof Oneadvantage of the present disclosure is that any catalyst preparationmethod can be employed provided that the substrate coating and thesubstrate itself can be processed separately from the catalyst andcatalyst support. Certain methods, such as, for example, aco-precipitation method, can be incompatible with certain substrate andsubstrate coating processing methods. The present disclosure can atleast partially overcome such limitations.

It should be appreciated that a catalyst on a substrate can be utilizedin the green or unfired state, such that upon exposure to operatingtemperatures, the materials utilized therein will become fixed orcalcined. In another aspect, a coated substrate and/or a supportedcatalyst on a substrate can be heated, dried, fired, and/or calcined atany point prior to or during use.

It should be understood that the method for providing a catalyst on asubstrate of the disclosure can be used in combination with the methods,products, and applications of the disclosure.

In various aspects, a coated substrate can be contacted with a solutionof catalyst before or after heating, drying, firing, and/or calciningthe coated substrate. In other aspects, one or more of the washcoatsdescribed herein can be catalytically active and/or can further comprisea catalyst, such that a washcoated substrate exhibits catalyticactivity.

In one aspect, a second washcoat, when applied to a coated substrate,can form a second layer coating. Such a second coating, in variousaspects, can be any suitable thickness and can be continuous ordiscontinuous over any portion of the whole of a substrate surface. In aspecific aspect, the second washcoat composition forms a continuouscoating. In another aspect, the second washcoat composition forms asubstantially uniform continuous coating on a coated substrate. In yetanother aspect, the second washcoat composition forms one or morediscrete coating regions on a coated substrate.

It should be understood that the catalyst of the disclosure can be usedin combination with the compositions, methods, products, andapplications of the disclosure.

With reference to FIG. 1, a supported catalyst on a substrate 100,prepared in accordance with various aspects of the present disclosure isillustrated. A substrate 140 coated with an anchor layer 130 from afirst washcoat is depicted. The coated substrate also comprises aplurality of supported catalyst particles 110 in a second layer, formedfrom a second washcoat. In FIG. 1, an exploded view of an exemplarysupported catalyst particle 110 is depicted, wherein the exploded viewof the exemplary supported catalyst particle located in the circulardotted line is illustrated above the substrate. Each of the plurality ofsupported catalyst particles 110 can comprise a plurality of individualcatalyst particles 120 positioned on the surface thereof. Each of theplurality of supported catalyst particles 110 can, depending upon thespecific material employed, also exhibit one or more bonding forces,150, such as, for example, hydrogen bonding. Such bonding forces, ifpresent, can facilitate bonding between the supported catalystparticles, anchor layer, and/or substrate.

Likewise, the substrate coating can be bound to a substrate through anyappropriate means. Examples include physical and chemical means.Specific examples include substrate coatings chemisorbed to thesubstrate, while other examples include substrate coatings physisorbedto the substrate, while still other examples include substrate coatingsboth chemisorbed and physisorbed to the substrate.

EXAMPLES

To further illustrate the principles of the present disclosure, thefollowing examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompositions, articles, and methods claimed herein are made andevaluated. They are intended to be purely exemplary of the disclosureand are not intended to limit the scope of what the applicants regard astheir disclosure. Efforts have been made to ensure accuracy with respectto numbers (e.g., amounts, temperatures, etc.); however, some errors anddeviations should be accounted for. Unless indicated otherwise,temperature is ° C. or is at ambient temperature, and pressure is at ornear atmospheric. There are numerous variations and combinations ofprocess conditions that can be used to optimize product quality andperformance. Only reasonable and routine experimentation will berequired to optimize such process conditions.

Example 1 Method for Making a Supported Catalyst for CO Oxidation(Prophetic)

In a first example, an active CuO—CeO₂ catalyst powder can be prepared.For selective CO oxidation, CuO—CeO₂ can be an active catalyst. ACuO—CeO₂ catalyst can typically be calcined at temperatures greater thanabout 600° C. It can be advantageous to calcine a supported catalyst inthe absence of a substrate, particularly if the substrate can beadversely affected at such a calcination temperature. The presentdisclosure can, for example, allow for a supported catalyst powder to beprocessed, calcined, and subsequently applied to a substrate or a coatedsubstrate.

The supported catalyst powder can be prepared by dissolving Cu(NO₃)₂ andCe(NO₃)₃ in water in an amount such that after calcination, CuO ispresent at about 5 wt. % of the total powder. A salt solution and NH₄OHcan be simultaneously added to water with stirring at a temperaturegreater than about 75° C., and preferably less than about 90° C. Theresulting precipitate can be allowed to age for about 1-2 hr, followedby centrifugation and washing. The precipitate powder can then be driedand calcined at about 700° C. for at least about 3 hr in air. The powdercan then be ground to an appropriate particle size, preferably less thanabout 5 μm.

A washcoat, which can produce a coating compatible with theaforementioned powder supported catalyst, can be prepared separately.For example, a slurry of finely grounded CeO₂ can be added to a solutionof Ce(NO₃)₃ dissolved in a polar organic solvent, such as, for example,diethylene glycol monoethyl ether, cellusolve, or a combination thereof.

A substrate, such as a monolith, can be coated with the slurry byexposing the substrate to the slurry solution. The resulting coatingsubstrate can then comprise a layer having properties such that theaforementioned powder supported catalyst can bind to the layer.

The coated substrate could then be exposed to a slurry of the powdersupported catalyst so as to produce a catalyst coating. The resultingsubstrate can then be dried and calcined at a temperature of, forexample, about 400° C. The particular catalyst loading can be affectedby the viscosity of the catalyst powder slurry. The viscosity of thecatalyst powder slurry can be lowered, if desired, through the additionof a polar organic solvent to the slurry and/or through the addition ofsurfactants.

Example 2 Method for Making a Supported Pd/Zn/Cu Catatlyst (Prophetic)

In a second example, a Pd/Zn/Cu based catalyst can be prepared. Incontrast to Example 1, ZnO can be used in lieu of CeO₂. In addition,Pd(NO₃)₂ can be added. The supported catalyst powder can be prepared bydissolving Ce(NO₃)₂, Zn(NO₃)₃, and Pd(NO₃)₃ in water, and the resultingsolution can be heated to a temperature of greater than about 60° C. Tothis solution, aqueous Na₂CO₃ can be slowly added to raise the pH to avalue greater than about 9 such that the salt begins to precipitate. Theprecipitated salt can then be aged for about 1-3 hr. The precipitate cansubsequently be centrifuged, washed, dried, and calcined at atemperature between about 350-500° C.

A coating solution, capable of producing a coating compatible with theaforementioned powder supported catalyst, can be prepared separately.For example, a slurry of finely grounded CuO—ZnO, having median particlesizes of less than about 5 μm, can be added to a solution of bothCu(NO₃)₃ and Zn(NO₃)₃ dissolved in a polar organic solvent, such as, forexample deithylene glycol monoethyl ether, cellusolve, or a combinationthereof. The concentration of the solution should be such that the Cu:Znratio in solution is approximately 1, and wherein the resultingprocessed powder will yield about 5-25 wt. % CuO—ZnO of the totalcomposition after calcination. An aqueous slurry of the Pd/Cu/ZnOcatalyst powder can then be made.

A substrate, such as a monolith, can be coated with the slurry byexposing the substrate to the slurry solution. The resulting coatedsubstrate can comprise a layer with properties such that the powdersupported catalyst can bind to the layer. The resulting coated substratecan then be dried.

Example3 Method for Making a Pd/Zn/Cu Supported Catalyst on a HighSurface Area Substrate (Prophetic)

In a third example, the procedure described above in Example 2 can beused to coat a high surface area substrate. In this example, a substratecoating can comprise γ-Al₂O₃. A slurry of γ-Al₂O₃ can be prepared in adiethylene glycol monoethyl ether solution, and can be combined withboehmite (AlOOH), such that the amount of boehmite present, aftercalcinations, is approximately equivalent to about 20 wt. % Al₂O₃ in theslurry. A substrate can be coated with the slurry, dried and calcined atabout 500° C. The catalyst coating can be prepared from any appropriatecatalyst, such as, for example, the catalyst of Example 2, Pd/Cu/ZnO.The resulting bilayered substrate can then be calcined.

Example 4 Method for Making a Supported Rh Catalyst (Prophetic)

In a fourth example, a supported Rh catalyst can be prepared usingmethods analogous to the methods disclosed in Examples 1-3. RhCl₃ can bedissolved in an aqueous solution, and the resulting solution can bemixed with γ-Al₂O₃, such that after drying and calcinations, thesupported catalyst comprises about 1 wt. % Rh/γ-Al₂O₃. With stirring, anaqueous solution comprising about 0.1 M Na₂CO₃ can be added to themixture to slowly raise the pH to greater than about 9, so as to induceprecipitation of Rh into the alumina suspension. The resultingprecipitate can be aged for about 1-3 hr, followed by centrifugation,washing, and drying to produce a catalyst powder. The resultant catalystpowder can then be calcined at about 450° C. for about 3 hr.

A slurry of γ-Al₂O₃ in diethylene glycol monoethyl ether can be mixedwith boehmite, AlOOH, such that the AlOOH after calcinations is presentin an amount approximately equivalent to about 20 wt. % Al₂O₃ in theslurry. A substrate, for example, a monolith, can be coated with theresulting slurry such that the coating layer is less than about 2 μmthick and preferably less than about 1 μm thick. The coated substratecan then be dried and calcined at about 500° C. The slurry of Rh/γ-Al₂O₃can then be added to the coated substrate and the resulting bilayersubstrate can be dried and calcined. In this example, the thin layer ofcoated Al₂O₃ can serve to provide (1) a high surface area and (2) aplurality of surface hydroxyl functional groups to disperse and/oranchor the catalyst. The hydrogen bonds formed between the coating layerand the catalyst layer can, in certain aspects, form into metal oxygenbonds at elevated temperatures.

Lastly, it should be understood that while the present disclosure hasbeen described in detail with respect to certain illustrative andspecific examples thereof, it should not be considered limited to such,as numerous modifications are possible without departing from the broadspirit and scope of the present disclosure as defined in the appendedclaims.

1. A method for providing a catalyst on a substrate, the methodcomprising: a) providing a first washcoat comprising a soluble washcoatsalt species, a polar organic solvent, and an insoluble particulatematerial; b) contacting the first washcoat with a substrate to form acoated substrate; and then c) contacting the coated substrate with asecond washcoat comprising an oxide or an oxide-supported catalyst tophysisorb, chemisorb, bond, or otherwise adhere the oxide or theoxide-supported catalyst to the coated substrate.
 2. The method of claim1, wherein the insoluble particulate material is an oxide.
 3. The methodof claim 1, wherein the soluble washcoat salt species and the insolubleparticulate material comprise a same cation.
 4. The method of claim 1,wherein the soluble washcoat salt species comprises an iron compound, acerium compound, a copper compound, an aluminum compound, a titaniumcompound, a silicon compound, a magnesium compound, a yttrium compound,a zirconium compound, a zinc compound, or a combination thereof.
 5. Themethod of claim 1, wherein the soluble washcoat salt species comprisesat least one of a nitrate, a halide, a carboxylate, or a combinationthereof.
 6. The method of claim 1, wherein the polar organic solventcomprises ethylene glycol monoethyl ether, ethylene glycol monomethylether, diethylene glycol monoethyl ether, cellusolve, or a combinationthereof.
 7. The method of claim 1, further comprising, at least one ofheating, drying, firing, calcining, or a combination thereof the coatedsubstrate.
 8. The method of claim 1, wherein the second washcoat is madeby combining a solvent and an oxide or an oxide-supported catalyst inpowder form.
 9. A catalyst on a substrate comprising: a) a substratehaving at least one surface; b) an anchor layer contacting at least aportion of the at least one surface, comprising: i. a soluble washcoatsalt species; ii. a polar organic solvent; and iii. an insolubleparticulate material; and c) a second layer positioned on at least aportion of the anchor layer oppositely disposed from the substrate,wherein the second layer comprises an oxide or an oxide-supportedcatalyst.
 10. The catalyst of claim 9, wherein the insoluble particulatematerial is an oxide, and wherein the insoluble particulate material andthe soluble washcoat salt species comprise a same cation.
 11. A catalyston a substrate comprising: a) a substrate having at least one surface;b) an anchor layer contacting at least a portion of the at least onesurface; and c) a second layer positioned on at least a portion of theanchor layer oppositely disposed from the substrate, wherein the anchorlayer comprises a first oxide, wherein the second layer comprises asecond oxide or an oxide-supported catalyst, and wherein both the anchorlayer and the second layer comprise substantially no binder.
 12. Thecatalyst of claim 11, wherein the first oxide and the second oxidecomprise a same cation.
 13. The catalyst of claim 11, wherein the firstoxide and the second oxide comprise a different cation.
 14. The catalystof claim 11, wherein at least one of the first oxide and/or the secondoxide comprises an iron compound, a cerium compound, a copper compound,an aluminum compound, a titanium compound, a silicon compound, amagnesium compound, a yttrium compound, a zirconium compound, a zinccompound, or a combination thereof.
 15. The catalyst of claim 11,wherein the substrate comprises a plurality of inner channels havingsurfaces defined by porous walls and extending through the substratefrom a first face to a second face.
 16. The catalyst of claim 15,wherein the substrate is a honeycomb monolith.
 17. The catalyst of claim1 1, wherein the first washcoat forms an anchor layer and the secondlayer comprise substantially no binder material.
 18. The catalyst ofclaim 11, wherein at least a portion of the anchor layer is capable ofhydrogen bonding to at least a portion of the second layer.
 19. Thecatalyst of claim 11, wherein the second layer is continuous.
 20. Thecatalyst of claim 11, wherein each of the anchor layer and the secondlayer has a thickness, and wherein a combination of the thickness of theanchor layer and the thickness of the second layer is less than about 5mm.